1. Field of the Invention
The present invention relates to an ice-making machine and an ice-making method, specifically a machine and a method for producing ice-slurry by forming a frozen layer inside a plurality of heat transfer pipes by allowing a liquid to be cooled to flow inside the pipes and a refrigerant liquid outside the pipes and scraping the frozen layer with a rotating rod rotating inside the pipes.
2. Description of the Related Art
Heretofore, an ice-making machine that is known as this kind is a machine for producing ice-slurry by forming a frozen layer inside a plurality of heat transfer pipes by allowing a liquid to be cooled to flow inside the pipes and a refrigerant liquid outside the pipes and scraping the frozen layer with a rotating rod (agitating bar) rotating inside the pipes (see Unexamined Published International Patent Application No. 9-501225). In the apparatus disclosed in the above Patent Application, a refrigerant is supplied to the outside of heat transfer pipes disposed upright and a liquid is supplied from the upper end of the heat transfer pipe to be frozen to form ice crystals in the popes. The ice crystals are mechanically removed by scraping the crystals with rotating rods rotating in the pipes. The scraped ice becomes slurry, which is re-circulated.
However, the ice-making machine of the prior art mentioned above has problems cited below. As a crank mechanism is provided for each of the agitating rod which revolves while rotating in each heat transfer pipe to scrape the ice crystal, the driving mechanism of the rods is complicated and a large number of parts are required.
Further, as the rotating rod is made of stainless steel, abrasion occurs due to the rubbing of the rod against the heat transfer pipe made of metal. As a result, the rotating rod and heat transfer pipe are damaged, and the attrition is further advanced by the tore-off matter due to the abrasion, the tore-off matter acting as abrasive.
Still further, as the diameter of the rotating rod is small compared with the inside diameter of the heat transfer pipe, the rotation speed of the rotating rod is relatively fast and the abrasion of the sliding face becomes severe.
Yet further, there are problems that, as the ice-making machine is of open type and the intrusion of air is premised, there occur air trapping into the liquid to be cooled inducing generation of bubbles, deterioration of the liquid, oxidation of the piping, dysfunction of pumping and transferring in the piping due to the trapped air as the water-with-ice mixed with air is to be transferred to a load side, leakage of sealing, and decreasing of heat transfer ability of the heat exchanger.
The present invention is made in the light of the problems mentioned above. An object of the invention is to provide an ice-making machine having an eccentric driving means, in which abrasion by the motion of a rotating rod is reduced and air is not induced.
Another object of the invention is to provide an ice-making method in which the detection of the state of freezing at the start and at the end of operation and in the heat transfer pipes is performed.
To attain the objects, an ice-making machine according to the present invention is provided with a plurality of heat transfer pipes and rotating rods each of which rotates in each of the heat transfer pipes disposed inside a shell, in which a liquid to be cooled is supplied to inside and a refrigerant liquid to outside the heat transfer pipes, ice crystals are formed on the inside surfaces of the heat transfer pipes through the cooling of the liquid to be cooled, and the ice crystals are scraped off with the rotating rods and taken out together with the liquid to be cooled, wherein the rotating rods which pass through the holes, the holes being larger in diameter than that of the rotating rods, of a driving plate connected with a revolving eccentric driving means provided on a driving shaft, revolve while rotating in the heat transfer pipes.
According to the above cited invention, as the rotating rods passing through the holes formed in a driving plate are driven by the driving plate revolved by the medium of an eccentric driving means provided on a driving shaft by means of the holes to revolve and at the same time to rotate, all of the rotating rods are driven by a single eccentric driving means in synchronization with each other. Therefore, an ice-making machine of closed type with a simplified eccentric driving means and a small number of constituent parts is obtained, leading to easy maintenance and operation free from the intrusion of air.
A simple mechanism of the eccentric driving means can be established by providing the driving shaft with an eccentric cam or a crank.
Further, by configuring the rotation rod as a metal rod provided with a plastic layer on the surface, preferably a plastic layer such as fluororesin having good sliding property with small friction resistance, metal-to metal contact is avoided and worn-off metal grains are embedded in the plastic layer, and less abrasion of the inside surface of the heat transfer pipe is effected.
Still further, according to the present invention, by attaching heat-insulating material on pipe end plates provided on both ends of a shell, the growth of ice frozen on the end plates inside headers is prevented.
Yet further, each of the rotating rods is supported at the head part formed at its upper end by a fixed plate attached to the shell, and a taper face formed on the lower periphery of the head part of each of the rotating rods sits on the taper face formed on the periphery of each of the penetrating holes on the fixed plate.
According to the invention cited above, as the taper face of the head part of the rotating rod contacts with the taper face of the hole of the fixed plate to slide on it, friction face of rotation becomes small and deformation and damage due to wear can be reduced.
Further, according to the present invention, the head part and lower end part of each of the rotating rods protrude into headers disposed at both end sides where the liquid to be cooled passes through and the liquid to be cooled passing through the headers is agitated by the revolving motion of the head part and lower end part of each of the rotating rods. Accordingly, the stagnation of ice in the headers is prevented by the stirring action of the head parts and lower end parts of the rotating rods.
Further, the present invention is characterized in that additional holes for the mixture of the liquid to be cooled and ice to flow through are formed on the driving plate and fixed plate. Therefore, the stagnation of ice grains between the plates is prevented. As the ice grains formed also flow through the additional holes in addition through crescent holes formed between the holes on the driving plate, fixed plate, and rotating rods, the biting of ice grains between the rotation sliding surfaces is reduced. Therefore, the erosion of the sliding faces of the holes and the rotating rods is suppressed.
Further, the present invention is able to be composed so that the rotating rods automatically move to the center side of the heat transfer pipes when frozen layer grows without being scraped off in the heat transfer pipes, by providing a slide cam for adjusting the amount of eccentricity between the driving plate and the driving shaft.
Further, in the present invention, it is possible to remove iron rust contained in the liquid to be cooled by allowing the rust to adhere to magnets provided on the inside periphery of the headers.
It is preferable to compose the present invention so that a shell is disposed horizontally, both ends of rotating rods are supported by driving plates, a balance weight driven by the driving shaft is disposed in the center part of the shell, and heat transfer pipes are immersed in refrigerant liquid filled in the shell. According to the invention, an ice-making machine without intrusion of air, generation of bubbles, and deterioration of brine because of its full-filled horizontal type, is constructed.
Further, an ice-making method according to the present invention is a method in which a liquid to be cooled is supplied to inside and a refrigerant liquid to outside the heat transfer pipes disposed in a shell ice crystals are formed on the inside surfaces of the heat transfer pipes through the cooling down of the liquid to be cooled, and the ice crystals are scraped off with the rotating rods and taken out together with the liquid to be cooled, wherein the liquid to be cooled and the refrigerant are flowed inside and outside the heat transfer pipes respectively; a driving motor is started to rotate with slow speed to rotate the rotating rods when the evaporation temperature of the refrigerant has become 0xc2x0 C. or below; when the freezing in the heat transfer pipes has advanced and the load for the driving motor has become larger than a certain value, the supply of the refrigerant is stopped and refrigerant gas is introduced from a refrigerator into the evaporating part of the shell to raise the evaporating temperature therein; after the evaporating temperature has risen to the freezing temperature or above of the liquid to be cooled, the operation of the refrigerator is stopped; and the operation of the refrigerator is restarted at the time the load for the driving motor recovered the initial value.
According to the above cited invention, as the driving motor is started with low rotation speed at first when the evaporating temperature of the refrigerant is 0xc2x0 C. or below and the rotation speed of the driving motor is increased at the time the freezing in the heat transfer pipes has advanced, the plastic layers formed on the surface of the rotating rods are prevented from melting in the early stages of the operation when the temperature of the rotating rods is high by rotating them with low speed, and the supply of the refrigerant and the liquid to be cooled is able to be controlled while detecting the degree of freeze in the course of freezing, ice grains are produced by automatic and safe operation.
Further, the present invention is characterized in that, when stopping the operation of the ice-making machine, at first the operation of the refrigerator is stopped, then the driving motor is stopped at the time the saturation temperature corresponding to the pressure at the evaporating part of the refrigerant has risen to equal or above the freezing temperature of the liquid to be cooled, and the supply of the liquid to be cooled is stopped at last.
According to the invention cited above, as the driving motor is stopped at the time the saturation temperature has risen to the freezing temperature or higher and the supply of the liquid to be cooled is ceased at last, automatic and safe operation is possible.